The present invention relates to a pull type installation tool and system for setting fasteners by a relative axial force applied to the fastener and more particularly to a high pressure, hydraulically actuated installation tool.
The pull tool of the present invention is directed to the installation of fasteners mainly of the two piece lockbolt or swage type such as that illustrated in U.S. Pat. No. 3,915,053 to J. Ruhl, issued Oct. 28, 1975, U.S. Pat. No. 2,531,048 to L. Huck, issued Nov. 21, 1950 and U.S. Pat. No. 4,208,943 to W. Smith, issued June 24, 1980.
As seen from the noted patents, lockbolts are installed by applying a relative axial force between a pin and a collar by the pull stroke of a piston-cylinder type tool; the tool has a jaw assembly to grip a pull portion of the pin and a swage anvil which engages the collar. When the relative axial force attains a preselected magnitude a swage cavity of the swage anvil moves over the collar moving the collar material radially inwardly into lockgrooves on the pin. The relative axial force increases until the pull or pintail portion of the pin is severed at a weakened breakneck groove. This completes the installation except for the removal of the tool from the swaged collar. With small diameter fasteners the swage cavity of the tool anvil can be constructed to be self releasing from the swaged collar in response to pin break; however, with larger diameter fasteners (from around 3/8 inch to as large as 13/8 inch nominal diameter of the pin shank) this may not be desirable because of the magnitude of recoil loads involved at pin break. Thus in the latter instance the tool is provided with a structure to provide ejection of the collar from the swage cavity of the tool by a reverse, relative axial pushing force applied to the collar on a return stroke of the tool.
Thus the present invention is more specifically directed to installation tools capable of developing significantly high (relative axial) pull loads i.e. from about 23,000 pounds pull for a 3/8 inch diameter fastener to about 110,000 pounds pull for a 13/8 inch diameter fastener (nominal shank diameter of the pin). Such tools are conventionally operable from a source of relatively high hydraulic pressure; in this regard, fluid pressures of from around 5,500 psi to around 8,500 psi are common.
As noted, the setting loads required by the tool increases as the size of the fastener increases and hence the tool size and weight increases as well. Thus with large diameter fasteners, i.e. a nominal pin diameter of around 3/8" and greater, the installation tools heretofore used can weigh from around 13 pounds for a tool for setting a 3/8" diameter fastener to around 65 pounds for a tool for setting a 13/8" diameter fastener; often times counterweight systems are required to facilitate manual handling of the tools.
It is common for such installation tools to utilize a single piston-cylinder arrangement. In the present invention it has been found that a significant weight and size reduction can be realized by utilizing a tandem, two piston-cylinder arrangement. At the same time a novel structure and porting system is provided whereby one of the two cylinders is defined and operative only on one side of its associated piston such that this piston-cylinder combination is effective only during the pull stroke operation of the tool. Thus both of the piston-cylinder combinations will be utilized to provide the high axial loads required for the installation of the fastener on the pull stroke while only one of the piston-cylinder combinations will be utilized to provide the lower loads for the return stroke and ejection of the collar from the swage cavity of the tool anvil. As will be seen, the result is an installation tool of a significantly reduced size and weight. Thus tools constructed in accordance with the present invention, by comparison to the weight of prior tools as noted above, will weigh around 4.5 pounds for a tool developing a 23,000 pound pull for setting a 3/8" diameter fastener to around 28.0 pounds for a tool developing a 110,000 pound pull for setting a 13/8" diameter fastener. In both cases the cylinders of the tools were essentially constructed of the same type of ferrous materials such as 4340 alloy steel.
In addition to the above, the installation tool of the present invention lends itself to a simplified construction facilitating its economical manufacture.
In the construction of pneumatically actuated tools for setting blind rivets, it is known to use multiple pistons and cylinders arranged in tandem especially where relatively low pneumatic pressures are anticipated. Examples of such tandem piston and cylinder constructions, which are pneumatically actuated, are shown in the following patents: U.S. Pat. Nos. 3,451,248 to W. Bell, issued June 24, 1969, 3,457,763 to R. B. Freeman, issued July 29, 1969, 3,523,441 to W. Bell et al, issued Aug. 11, 1970, 3,557,597 to V. L. Heslop et al, issued Jan. 26, 1971, 3,714,810 to C. R. Boyd, issued Feb. 6, 1973, 4,259,858 to R. B. Freeman, issued Apr. 7, 1981. Structures of the type shown in these patents, however, are not directed to the same problems as the high pressure, high relative axial pull load, hydraulically actuated tools of the present invention.
Thus it is an object of the present invention to provide a novel installation tool and system for setting fasteners by the application of a relative axial force with the tool having a novel tandem piston-cylinder construction whereby a significant reduction in size and weight can be realized over tool constructions heretofore used for such applications.
It is another object of the present invention to provide a novel pull type installation tool and system having a tandem piston-cylinder construction in which less than all of the piston-cylinders are utilized for collar ejection on a return stroke whereby a compact, lightweight construction can be utilized.
It is another object of the present invention to provide an installation tool construction which is of a simplified construction permitting it to be manufactured economically.
It is a general object of the present invention to provide a novel pull type installation tool having a compact, lightweight construction.